This invention relates generally to stators for dynamoelectric machines and, more particularly, to methods and apparatus for winding conductive wires for such stators.
The stator of a dynamoelectric machine such as an electric motor or generator typically includes a core of magnetic material having an axially extending bore for receiving a rotor. The core typically is formed from a plurality of identical laminations which are aligned and arranged in a stack held together by clips. Each lamination includes a plurality of teeth which extend radially into the bore. Slots between each of the teeth extend radially outwardly from the bore. The ends of the teeth and the open ends of the slots define the periphery of the bore.
A plurality of coils formed from insulated conductive wire are inserted into selected core slots with portions of the coils at the ends of the core forming end turn regions. The coils are interconnected to form coil groups or poles. The conductive wires which form the coils, sometimes referred to as stator windings, typically are coated with a varnish or an enamel so that a tough protective coating is formed around each wire. The coating is required so that each wire is well insulated from the other wires.
A single speed motor typically includes coil groups which establish at least one main winding and an auxiliary or start winding. The coil groups are formed with a winding machine and located on coil insertion (or injection) tooling. The coil groups are then injected into the stator, e.g., moved from the coil insertion tooling to the stator, so that coil portions substantially aligned with stator core slots are injected into such slots.
To form each coil, conductive wire is inserted into the winding machine and coupled to a winding machine needle. The winding machine needle then extracts the conductive wire so that the extracted wire is coiled. The tension of the conductive wire typically fluctuates while coiling the wire. Particularly, each time the winding needle changes direction to form the coil, some slack occurs in the conductive wire. This fluctuating tension sometimes causes the conductive wire to break. In addition, this fluctuating tension sometimes results in loose windings being injected into the stator, which is undesirable.
It would be desirable to provide an apparatus for reducing tension fluctuation while coiling conductive wires. It also would be desirable for such apparatus to be simple to fabricate and utilize.
These and other objects may be attained by a hysteretic tensioning apparatus which, in one form, substantially stabilizes tension in conductive wires supplied to a winding machine. The hysteretic tensioning apparatus includes a support member, a brake member, and at least one idler arm. The brake member is rotatably mounted to the support member adjacent a first side thereof and is rotatable relative to the support member. The idler arm is spring mounted to the support member adjacent a second side thereof and also is configured to engage. the conductive wire.
The hysteretic tensioning apparatus is positioned so that the conductive wire moves through the apparatus during a winding operation. Particularly, the conductive wire enters the hysteretic tensioning apparatus and extends between the brake member and the idler arm. The wire then exits the hysteretic tensioning apparatus and is supplied to the winding machine. The brake member and idler arm cooperate to substantially alleviate any slack from occurring from reversing direction of the winding needle, and thus substantially prevent loose windings on the stator and wire breakage during the winding operation.
The above described hysteretic tensioning apparatus reduces tension fluctuation in a conductive wire while coiling the conductive wire. Such apparatus also is believed to be simple to fabricate and utilize.